* The distribution of rain in Doha is usually rather uneven, thanks to the nature of the storms that we get here INSET: * Ganeshkumar, a class 9 student of DPS-MIS, took photographs of the enormous raindrops that fell on May 4. Here he has shared the pictures for the benefit of the readers.

By Steff Gaulter

It’s been rather wet in Doha recently, I think you’ll agree. The huge thunderstorms on May 4 brought enormous raindrops which fell hard and fast. They bounced high off the ground, and turned the streets into swimming pools in just a few hours. Officially 14mm (0.6 inches) of rain fell, but as usual the rain across Doha was patchy and some neighbourhoods saw far more than others.

A friend of mine who has a weather station on his roof told me that as much as 30mm (1.2 inches) of rain poured in the Old Airport region. Elsewhere people reported hail, and no one could miss hearing the crashes of thunder.

The distribution of rain in Doha is usually rather uneven, thanks to the nature of the storms that we get here. The majority of rain that falls in Qatar is produced from cumulus clouds, the fluffy ones with the tops that look like cauliflowers. They’re formed by convection, the mixing of air caused by uneven heating.

The hot ground heats the air near it, and as most of us know, hot air rises. As it rises, it cools and the water in the air condenses into droplets of water.

Whether it then develops into a huge towering thunderstorm, or peters out again like a damp squib, depends on many little factors, including how hot the ground is and how much moisture is in the air.

The processes that determine how much a convective cloud can grow are so small that they can’t be modelled by computers. At present it’s impossible to model an individual thunderstorm; computers will have to become far more powerful before this is feasible.

Many of us enjoyed the unusual weather, but some were keen to see the end of the thunderstorms, particularly those who had friends visiting. Obviously there are more things to do in Qatar when it’s not throwing it down, but there is also another reason why we should hope for calm weather when we have friends visiting: thunderstorms can cause turbulence.

Very few people like a bumpy aeroplane ride. In fact I could be the only person who actually does, and even I don’t like the really extreme shaking! If the plane is gently rocked by turbulence, it has a habit of putting me to sleep. Other people find it absolutely petrifying. On one flight from Florida to New York, I really had to struggle to stay awake to calm down my friend who was convinced the plane was about to fall out the sky.

Turbulence isn’t only found within a cumulus cloud, it’s also found around it too. Although we can only see the clouds, around it we know that the air is also swirling and mixing, and it’s this movement which causes turbulence. As you may well have noticed, small aircraft often feel the effect of turbulence more severely than larger ones. This is similar to the movement of a small boat which will bob around in the ocean more violently than a huge cruise liner.

Turbulence can also be caused by the ground. As the air flows through the atmosphere, there’s not really a great deal to slow it down, except near the ground. The terrain can act as a break, causing the air near it to slow and swirl. If the wind is strong and the ground is hilly, then the turbulence can be quite strong. Mountains also cause turbulence if the air sweeping over it ‘rolls’ over their peaks. A friend who works for the UK Met Office was once stationed on the Falkland Isles. He was taken up in one of the RAF jets: a small aircraft and mountainous terrain, the recipe for severe turbulence.  

The jet shot through the air, buffeted about by rolling air. When they reached terra firma again, my friend was as green as the grass. The pilot took one look at him and said, “I’m impressed. You’re the first person I’ve ever taken up who hasn’t actually been sick.” The turbulence my friend experienced on that flight is worse than anything any of us are likely to experience on a commercial airliner.

Knowing this certainly helps me relax when my plane experiences a bit of a bumpy patch of air.

There is one other type of turbulence, which is arguably the most dangerous kind. It is undetectable and is completely invisible; there are no mountains or cumulus clouds to indicate that there might be turbulence in the vicinity. This ‘clear air turbulence’, or CAT, can be found more or less anywhere, and it’s very common at the altitude at which aircraft fly.

A new theory suggests that there will be more CAT as the climate continues to change. This is because although the air around us is warming, the air in the stratosphere, the level above that in which our weather happens, is actually cooling. As the contrast in the temperatures increases, so will the amount of turbulence. There is evidence that CAT has already risen by between 40 and 90% over Europe and North America since 1958, and studies need to be completed to confirm they have risen elsewhere as well.

If the amount of turbulence does rise as predicted, it’s worth bearing in mind that most injuries happen when the turbulence strikes suddenly and passengers are not wearing their seatbelts. The sharp movement means that people can hit their heads on the aircraft’s ceiling.

As the climate continues to change maybe we should pay more attention to the pilot when he advises us to keep our seatbelts securely fastened, even if the seatbelt sign isn’t on. He might just be right.

(The author is Senior Weather Presenter at Al Jazeera English channel. She can be contacted on steff.gaulter@yahoo.co.uk
or on Twitter at @WeatherSteff)